Manufacturing method of circuit board

ABSTRACT

A manufacturing method of a circuit board is provided. Providing a substrate, where a first laser resistant structure is disposed on a first dielectric layer and at the periphery of a pre-removing area, a second dielectric layer covers the first laser resistant structure, a circuit layer is disposed on the second dielectric layer, a second laser resistant structure is disposed on the second dielectric layer and at the periphery of the pre-removing area, a third dielectric layer covers the circuit layer and the second laser resistant structure. There are gaps between the second laser resistant structure and the circuit layer, and the vertical projection of the gaps on the first dielectric layer overlaps the first laser resistant structure. A laser machining process is performed to etch the third dielectric layer at the periphery of the pre-removing area. The portion of the third dielectric layer within the pre-removing area is removed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of and claims prioritybenefit of an U.S. application Ser. No. 12/752,376, filed on Apr. 1,2010, now pending, which claims the priority benefit of Taiwanapplication serial no. 98111066, filed on Apr. 2, 2009. The entirety ofeach of the above-mentioned patent applications is hereby incorporatedby reference herein and made a part of specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a circuit board and amanufacturing method thereof, and more particularly, to a circuit boardand a manufacturing method thereof with effective laser machining depthcontrol.

2. Description of Related Art

Today's market demands electronic products to be designed small, slim,light, and highly portable. Accordingly, electronic parts in theseelectronic products have to be designed small and thin too. Thereby, aconventional technique for reducing the thickness of a portion of acircuit board is provided.

FIGS. 1A-1C are cross-sectional views illustrating a conventionalcircuit board manufacturing process, and FIG. 2 is a top view of acircuit substrate in FIGS. 1A-1C, wherein FIGS. 1A-1C arecross-sectional views illustrating the conventional circuit boardmanufacturing process along line I-I′ in FIG. 2.

First, referring to both FIG. 1A and FIG. 2, a circuit substrate 100having a first dielectric layer 110, a second dielectric layer 120, acircuit layer 130, a third dielectric layer 140, and a fourth dielectriclayer 150 is provided. The second dielectric layer 120, the thirddielectric layer 140, and the fourth dielectric layer 150 aresequentially stacked on the first dielectric layer 110, and the circuitlayer 130 is disposed on the second dielectric layer 120 and locatedbetween the second dielectric layer 120 and the third dielectric layer140. The circuit substrate 100 has a pre-removing area L.

Then, referring to FIG. 1B, the portions of the third dielectric layer140 and the fourth dielectric layer 150 located at the periphery of thepre-removing area L are removed through laser machining. Next, referringto FIG. 1 C, the portions of the third dielectric layer 140 and thefourth dielectric layer 150 located within the pre-removing area L areremoved to form a removing area L1. Herein a circuit board P is roughlyformed. Because the removing area L1 of the circuit board P is thinnerthan other areas of the circuit board P, an electronic device 200 may bedisposed within the removing area L1 in an actual application to reducethe total thickness of the circuit board P and the electronic device 200disposed thereon.

However, it is difficult to control the depth of the laser machiningwhen the third dielectric layer 140 and the fourth dielectric layer 150are removed through laser machining. As a result, the second dielectriclayer 120 or even the first dielectric layer 110 may be over trenched.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a circuit board, andmore particularly, to a circuit board structure with effective lasermachining depth control.

The present invention is further directed to a manufacturing method of acircuit board, wherein the laser machining depth is effectivelycontrolled.

The present invention provides a circuit board having a removing area.The circuit board includes a first dielectric layer, a first laserresistant structure, a second dielectric layer, a circuit layer, asecond laser resistant structure, and a third dielectric layer. Thefirst laser resistant structure is disposed on a first surface of thefirst dielectric layer and located at the periphery of the removingarea. The second dielectric layer is disposed on the first dielectriclayer and covers the first laser resistant structure. The circuit layeris disposed on a second surface of the second dielectric layer, and aportion of the circuit layer is extended from outside of the removingarea into the removing area. The second laser resistant structure isdisposed on the second surface and located at the periphery of theremoving area, and the second laser resistant structure is insulatedfrom the circuit layer. There is at least one gap between the secondlaser resistant structure and the circuit layer, and the verticalprojection of the gap on the first surface overlaps the first laserresistant structure. The third dielectric layer is disposed on thesecond dielectric layer and has an opening corresponding to the removingarea, wherein the opening exposes the portions of the circuit layerlocated within the removing area. The third dielectric layer covers aportion of the second laser resistant structure.

According to an embodiment of the present invention, the second laserresistant structure is an annular structure, wherein the annularstructure has at least one nick, and the circuit layer is extended fromthe nick into the removing area.

According to an embodiment of the present invention, the first laserresistant structure includes a plurality of punctual structuresindependent from each other when there are multiple gaps between thesecond laser resistant structure and the circuit layer.

According to an embodiment of the present invention, the first laserresistant structure includes a strip structure.

According to an embodiment of the present invention, the strip structureoverlaps the vertical projection of the second laser resistant structureon the first surface.

According to an embodiment of the present invention, the seconddielectric layer has at least one cavity located below the gap.

According to an embodiment of the present invention, the cavity exposesthe first laser resistant structure.

According to an embodiment of the present invention, the circuit boardfurther includes a third laser resistant structure, wherein the thirdlaser resistant structure is disposed on the second surface and locatedat the periphery of the pre-removing area, and the third laser resistantstructure is connected with the portion of the circuit layer located atthe periphery of the removing area and is insulated from the secondlaser resistant structure.

According to an embodiment of the present invention, the circuit boardfurther includes a protection layer, wherein the protection layer coversthe portion of the circuit layer located within the removing area.

According to an embodiment of the present invention, the opening exposesa portion of the second laser resistant structure located within theremoving area.

The present invention provides a manufacturing method of a circuitboard. First, a substrate having a pre-removing area is provided. Thesubstrate includes a first dielectric layer, a first laser resistantstructure, a second dielectric layer, a circuit layer, a second laserresistant structure, and a third dielectric layer. The first laserresistant structure is disposed on a first surface of the firstdielectric layer and located at the periphery of the pre-removing area.The second dielectric layer is disposed on the first dielectric layerand covers the first laser resistant structure. The circuit layer isdisposed on a second surface of the second dielectric layer, and aportion of the circuit layer is extended from outside of thepre-removing area into the pre-removing area. The second laser resistantstructure is disposed on the second surface and located at the peripheryof the pre-removing area, and the second laser resistant structure isinsulated from the circuit layer. There is at least one gap between thesecond laser resistant structure and the circuit layer, and the verticalprojection of the gap on the first surface overlaps the first laserresistant structure. The third dielectric layer is disposed on thesecond dielectric layer and covers the circuit layer and the secondlaser resistant structure. Then, a laser machining process is performedto etch the third dielectric layer located at the periphery of thepre-removing area. Next, the portion of the third dielectric layerlocated within the pre-removing area is removed.

According to an embodiment of the present invention, the laser machiningprocess further includes etching the portion of the second dielectriclayer located below the gap.

According to an embodiment of the present invention, the laser machiningprocess does not etch the first dielectric layer.

According to an embodiment of the present invention, the technique ofremoving the third dielectric layer includes a lift-off technique.

According to an embodiment of the present invention, the second laserresistant structure is an annular structure, wherein annular structurehas at least one nick, and the circuit layer is extended from the nickinto the pre-removing area.

According to an embodiment of the present invention, the first laserresistant structure includes a plurality of punctual structuresindependent from each other when there are multiple gaps between thesecond laser resistant structure and the circuit layer.

According to an embodiment of the present invention, the first laserresistant structure includes a strip structure.

According to an embodiment of the present invention, the strip structureoverlaps the vertical projection of the second laser resistant structureon the first surface.

According to an embodiment of the present invention, the substratefurther includes a third laser resistant structure, the third laserresistant structure is disposed on the second surface and located at theperiphery of the pre-removing area, and the third laser resistantstructure is connected with the portion of the circuit layer located atthe periphery of the removing area and is insulated from the secondlaser resistant structure.

According to an embodiment of the present invention, the substratefurther includes a protection layer, wherein the protection layer coversthe portion of the circuit layer located within the pre-removing area.

According to an embodiment of the present invention, the manufacturingmethod further comprises performing an etching process to remove thesecond laser resistant structure.

According to an embodiment of the present invention, the manufacturingmethod further comprises performing a mechanical processing to remove aportion of the second laser resistant structure located within thepre-removing area.

According to an embodiment of the present invention, the manufacturingmethod further comprises performing an etching process to remove thefirst laser resistant structure.

According to an embodiment of the present invention, the manufacturingmethod further comprises performing a mechanical processing to removethe first laser resistant structure.

The present invention provides a circuit board having a removing area.The circuit board comprises a first dielectric layer, a circuit layer, alaser resistant structure, and a second dielectric layer. The circuitlayer is disposed on a surface of the first dielectric layer, wherein aportion of the circuit layer is extended from outside of the removingarea into the removing area. The laser resistant structure is disposedon the surface, located at the periphery of the removing area, andinsulated from the circuit layer, wherein there is at least one gapbetween the laser resistant structure and the circuit layer. The seconddielectric layer is disposed on the first dielectric layer, and has anopening corresponding to the removing area, wherein the opening exposesa portion of the circuit layer located within the removing area.

As described above, in the present invention, the circuit board has afirst laser resistant structure and a second laser resistant structuresuch that the depth of laser machining can be controlled through thesecond laser resistant structure, and the first dielectric layer underthe first laser resistant structure is protected by the first laserresistant structure from the laser machining process.

In order to make the above and other features and advantages of thepresent invention more comprehensible, several embodiments accompaniedwith figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIGS. 1A-1C are cross-sectional views illustrating a conventionalcircuit board manufacturing process.

FIG. 2 is a top view of a circuit substrate in FIGS. 1A-1C.

FIGS. 3A-3D′ and FIGS. 4A-4C are cross-sectional views illustrating acircuit board manufacturing process according to an embodiment of thepresent invention.

FIG. 5 is a top view of a circuit layer and a second laser resistantstructure of a substrate in FIGS. 3A-3C and FIGS. 4A-4C.

FIG. 6 is a top view of a first laser resistant structure of a substratein FIGS. 3A-3C and FIGS. 4A-4C.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

FIGS. 3A-3D′ and FIGS. 4A-4C are cross-sectional views illustrating acircuit board manufacturing process according to an embodiment of thepresent invention. FIG. 5 is a top view of a circuit layer and a secondlaser resistant structure of a substrate in FIGS. 3A-3C and FIGS. 4A-4C.FIG. 6 is a top view of a first laser resistant structure of thesubstrate in FIGS. 3A-3C and FIGS. 4A-4C.

It should be noted that the position of the line IT in FIG. 5 iscorresponding to the position of the line I-I′ in FIG. 6, and FIGS.3A-3C are cross-sectional views illustrating a circuit boardmanufacturing process along the lines I-I′ in FIG. 5 and FIG. 6according to an embodiment of the present invention. The position of theline II-II′ in FIG. 5 is corresponding to the position of the lineII-II′ in FIG. 6, and FIGS. 4A-4C are cross-sectional views illustratinga circuit board manufacturing process along the lines II-II′ in FIG. 5and FIG. 6 according to an embodiment of the present invention.

First, referring to FIGS. 3A, 4A, 5, and 6, a substrate S having apre-removing area L is provided. The substrate S includes a firstdielectric layer 310, a first laser resistant structure 320, a seconddielectric layer 330, a circuit layer 340, a second laser resistantstructure 350, and a third dielectric layer 360.

The first laser resistant structure 320 is disposed on a first surface312 of the first dielectric layer 310 and located at the periphery ofthe pre-removing area L. The second dielectric layer 330 is disposed onthe first dielectric layer 310 and covers the first laser resistantstructure 320. The circuit layer 340 is disposed on a second surface 332of the second dielectric layer 330, and a portion of the circuit layer340 is extended from outside of the pre-removing area L into thepre-removing area L.

The second laser resistant structure 350 is disposed on the secondsurface 332 and located at the periphery of the pre-removing area L andis insulated from the circuit layer 340. A portion of the second laserresistant structure 350 is located in the pre-removing area L andanother portion of the second laser resistant structure 350 is locatedoutside of the pre-removing area L. There is a plurality of gaps Gbetween the second laser resistant structure 350 and the circuit layer340, and the vertical projection of the gaps G on the first surface 312overlaps the first laser resistant structure 320.

The third dielectric layer 360 is disposed on the second dielectriclayer 330 and covers the circuit layer 340 and the second laserresistant structure 350. In the present embodiment, the substrate Sfurther includes a fourth dielectric layer 370 disposed on the thirddielectric layer 360.

In the present embodiment, the substrate S further includes a protectionlayer 380. The protection layer 380 covers the portion of the circuitlayer 340 located within the pre-removing area L so that the circuitlayer 340 will not be affected by the subsequent removal of the thirddielectric layer 360 and the fourth dielectric layer 370.

Next, referring to FIGS. 3B, 4B, 5, and 6, a laser machining process isperformed to etch the third dielectric layer 360 and the fourthdielectric layer 370 located at the periphery of the pre-removing areaL. Through the laser machining process, a plurality of cavities T isformed on the third dielectric layer 360 and the fourth dielectric layer370, and these cavities T expose the second laser resistant structure350 and the circuit layer 340 located at the periphery of thepre-removing area L.

To be specific, the laser machining takes place at the periphery of thepre-removing area L (i.e., the area L marked with dotted lines in FIG. 5and FIG. 6). Thus, a laser beam passing through the third dielectriclayer 360 and the fourth dielectric layer 370 is blocked by the secondlaser resistant structure 350. Accordingly, in the present embodiment,the depth of the laser machining can be controlled through the secondlaser resistant structure 350, and accordingly the production yield canbe improved.

In addition, to improve the performance of the second laser resistantstructure 350 in laser machining blocking, in the present embodiment,the width D of the second laser resistant structure 350 is designed tobe greater than the radian of the laser beam. Thus, ideally, thecavities T only expose the portion of the second laser resistantstructure 350 located at the periphery of the pre-removing area L.

It should be noted that in the present embodiment, the substrate S hasthe first laser resistant structure 320, and when a laser beam passesthrough the second dielectric layer 330 below the gaps G, the laser beamis blocked by the first laser resistant structure 320 below the gaps G.Thus, the first laser resistant structure 320 can protect the firstdielectric layer 310 below the first laser resistant structure 320 fromthe laser machining and help to control the depth of the lasermachining. Herein the laser machining process may form cavities 334 onthe second dielectric layer 330 below the gaps G.

Thereafter, referring to FIGS. 3C, 4C, 5, and 6, the portions of thethird dielectric layer 360 and the fourth dielectric layer 370 locatedwithin the pre-removing area L are removed to form a removing area L1wherein the third dielectric layer 360 covers a portion of the secondlaser resistant structure 350. The third dielectric layer 360 and thefourth dielectric layer 370 may be removed through a lift-off technique.In the present embodiment, the protection layer 380 is removed.

Referring to FIG. 3D, in the present embodiment, a portion of the secondlaser resistant structure 350 located within the removing area L1 isremoved through a mechanical processing. In addition, a portion of thefirst laser resistant structure 320 is removed through a mechanicalprocessing.

Referring to FIG. 3D′, in the other embodiment, the second laserresistant structure 350 is removed through an etching processing. Inaddition, the first laser resistant structure 320 is removed through anetching processing.

Below, the structure of the circuit board 300 will be described indetail.

Referring to FIGS. 3C, 4C, 5, and 6, in the present embodiment, thecircuit board 300 has a removing area L1, wherein the removing area L1is a depressed area. The circuit board 300 includes a first dielectriclayer 310, a first laser resistant structure 320, a second dielectriclayer 330, a circuit layer 340, a second laser resistant structure 350,and a third dielectric layer 360.

The first laser resistant structure 320 is disposed on a first surface312 of the first dielectric layer 310 and located at the periphery ofthe removing area L1. The second dielectric layer 330 is disposed on thefirst dielectric layer 310 and covers the first laser resistantstructure 320. The circuit layer 340 is disposed on a second surface 332of the second dielectric layer 330, and a portion of the circuit layer340 is extended from outside of the removing area L1 into the removingarea L1.

In the present embodiment, the circuit board 300 includes a plurality ofthird laser resistant structures 390. The third laser resistantstructures 390 are disposed on the second surface 332 and located at theperiphery of the removing area L1. The third laser resistant structures390 are connected with the portion of the circuit layer 340 located atthe periphery of the removing area L1 and are insulated from the secondlaser resistant structure 350.

The second laser resistant structure 350 is disposed on the secondsurface 332 and located at the periphery of the removing area L1, andthe second laser resistant structure 350 is insulated from the circuitlayer 340. There are a plurality of gaps G between the second laserresistant structure 350 and the circuit layer 340, and the verticalprojection of the gaps G on the first surface 312 overlaps the firstlaser resistant structure 320.

In order to improve the performance of the first laser resistantstructure 320 in the laser machining blocking, in the presentembodiment, the size of the first laser resistant structure 320 isdesigned to be larger than the area of the vertical projection of thegaps G on the first surface 312 so that the vertical projection of thegaps G on the first surface 312 can completely fall on the first laserresistant structure 320. Additionally, in the present embodiment, thesecond dielectric layer 330 may have multiple cavities 334 located belowthe gaps G. The cavities 334 expose the first laser resistant structure320.

To be specific, in the present embodiment, the second laser resistantstructure 350 is an annular structure. The annular structure has aplurality of nicks B, and a portion of the circuit layer 340 is extendedfrom the nicks B into the removing area L1. Besides, in the presentembodiment, the first laser resistant structure 320 may be a pluralityof punctual structures independent from each other. In otherembodiments, the first laser resistant structure 320 may be a stripstructure or an annular structure, and the strip structure or theannular structure may overlap the vertical projection of the secondlaser resistant structure 350 on the first surface 312.

The third dielectric layer 360 is disposed on the second dielectriclayer 330 and has an opening O corresponding to the removing area L1. Inthe present embodiment, the circuit board 300 further includes a fourthdielectric layer 370. The fourth dielectric layer 370 is disposed on thethird dielectric layer 360 and has an opening O1 corresponding to theopening O. The openings O and O1 expose the portions of the circuitlayer 340 and the second laser resistant structure 350 located withinthe removing area L1. Moreover, in the present embodiment, a protectionlayer 380 may be disposed within the removing area L1, wherein theprotection layer 380 covers the portion of the circuit layer 340 locatedwithin the removing area L1 to protect the circuit layer 340 exposed bythe openings O and O1.

It should be noted that even though one removing area L1 is described asan example in the present embodiment, the present invention is notlimited thereto. For example, in other embodiments, the circuit boardmay also have multiple removing areas, and these removing areas may beselectively located at the same side or two opposite sides of thecircuit board.

As described above, a circuit board provided by the present inventionhas a first laser resistant structure and a second laser resistantstructure such that the depth of the laser machining can be controlledthrough the second laser resistant structure. Besides, the firstdielectric layer below the first laser resistant structure is protectedby the first laser resistant structure from the laser machining

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A manufacturing method of a circuit board,comprising: providing a substrate, wherein the substrate has apre-removing area, and the substrate comprises: a first dielectriclayer; a first laser resistant structure, disposed on a first surface ofthe first dielectric layer and located at a periphery of thepre-removing area; a second dielectric layer, disposed on the firstdielectric layer and covering the first laser resistant structure; acircuit layer, disposed on a second surface of the second dielectriclayer, wherein a portion of the circuit layer is extended from outsideof the pre-removing area into the pre-removing area; a second laserresistant structure, disposed on the second surface, located at theperiphery of the pre-removing area, and insulated from the circuitlayer, wherein there is at least one gap between the second laserresistant structure and the circuit layer, and a vertical projection ofthe gap on the first surface overlaps the first laser resistantstructure; a third dielectric layer, disposed on the second dielectriclayer, and covering the circuit layer and the second laser resistantstructure; performing a laser machining process to etch the thirddielectric layer located at the periphery of the pre-removing area; andremoving a portion of the third dielectric layer located within thepre-removing area.
 2. The manufacturing method according to claim 1,wherein the laser machining process further comprises etching a portionof the second dielectric layer located below the gap.
 3. Themanufacturing method according to claim 1, wherein the technique ofremoving the third dielectric layer comprises a lift-off technique. 4.The manufacturing method according to claim 1, wherein the second laserresistant structure is an annular structure, the annular structure hasat least one nick, and the circuit layer is extended from the nick intothe pre-removing area.
 5. The manufacturing method according to claim 1,wherein the first laser resistant structure comprises a plurality ofpunctual structures independent from each other when there are multiplegaps between the second laser resistant structure and the circuit layer.6. The manufacturing method according to claim 1, wherein the firstlaser resistant structure comprises a strip structure or an annularstructure and the strip structure or the annular structure overlaps avertical projection of the second laser resistant structure on the firstsurface.
 7. The manufacturing method according to claim 1, wherein thesubstrate further comprises a third laser resistant structure, the thirdlaser resistant structure is disposed on the second surface and locatedat the periphery of the pre-removing area, and the third laser resistantstructure is connected with a portion of the circuit layer located atthe periphery of the pre-removing area and is insulated from the secondlaser resistant structure.
 8. The manufacturing method according toclaim 1, wherein the substrate further comprises a protection layer, andthe protection layer covers a portion of the circuit layer locatedwithin the pre-removing area.
 9. The manufacturing method according toclaim 1 further comprising: performing an etching process or amechanical processing to remove the second laser resistant structure.10. The manufacturing method according to claim 1 further comprising:performing an etching process or a mechanical processing to remove thefirst laser resistant structure.